Address Classes and Their Ranges
Understand the classful A, B, and C ranges and their use.
The Classful Idea
Before flexible masks, IPv4 used classful addressing. The first bits of an address placed it into a class — A, B, C, D, or E — and the class fixed how much of the address was network versus host.
Although modern networks use classless addressing (CIDR), the Network+ exam still expects you to recognize the classes and their ranges.
Class A Range
Class A covers first octets 1 to 126. It uses an 8-bit network portion and a 24-bit host portion, giving very large networks with millions of hosts each.
Its default mask is 255.0.0.0, also written /8. Class A was meant for the largest organizations and was assigned sparingly.
All lessons in this course
- Reading a Dotted-Decimal Address
- Network Portion vs Host Portion
- Address Classes and Their Ranges
- Public, Private, and Loopback Addresses